Miami officials found significantly higher levels of soil contamination than earlier detected in a playground at a popular Coconut Grove park and for the first time discovered at least one of the toxic chemicals has seeped into the groundwater.

A report released Tuesday by the county’s environmental office concludes that solid waste dumped years ago at Blanche Park at 3045 Shipping Ave. and buried beneath a layer of artificial turf has tainted soil in the playground with heavy metals, sometimes at 40 to 50 times acceptable levels. Two monitoring wells dug as part of the testing also revealed groundwater with elevated levels of antimony, a chemical used in paints, ceramics, glass and batteries, and which can cause lung and heart disease.

Despite the findings, officials have kept the park open and do not consider it dangerous because the artificial turf over the playground acts as a protective cap.

The results have been handed over to state health officials, who will determine whether any steps need to be taken to address health concerns, said Luis Espinoza, a spokesman for county environmental chief, Wilbur Mayorga, who was not available for comment.

Of the 11 spots tested in the playground, workers found heavy metals in 10 locations and dioxins, highly toxic carcinogens, in three. In the adjacent dog park, they found a handful of samples with elevated levels of arsenic, but at far lower amounts.

Because most of the contamination is two to four feet below ground and covered with turf, today’s park users don’t necessarily need to worry about exposure, said Gurpal S. Toor, a University of Florida associate professor of Environmental Soil Chemistry and Water Quality.

But “these heavy metals are not going to disappear magically from the site,” he said in an email. “If the groundwater table increases, it can potentially mobilize the metals and contaminate water. Again, this is not a direct concern for park users, but important for protecting our sensitive groundwater/aquifer.”

Sampling focused on the playground area, where workers found the largest deposits of waste typical of ash. The city purchased the site in 1943 to use as a dump and an ash pit from a nearby municipal incinerator. It converted the land to a park in 1962, but did not remediate the soil, as federal mandates on treating the soil weren’t established until much later.

Waste was first found on the parking lot surface as well as beneath the turf and in about nine inches of soil in the playground. Almost all the heavy metals were where ash was also found, the report said. The new tests show visible signs of solid waste and elevated levels of metals throughout the playground, including arsenic, barium, copper, iron and lead. Cadmium was found below exposure limits in soil, but above rates set for possible leaching into groundwater.

And while dioxins above acceptable levels were detected in the playground — in both the southwest and northeast corners — they were not high enough to pose any real danger to groundwater, Toor said.

Exposure to high amounts of dioxins are known to increase risks of cancer and may cause developmental and reproductive problems, according to the National Institute of Environmental Health Sciences.

“In any solid waste contaminated site, dioxins are generally higher. But dioxins are strongly retained/fixed in the soil, so the potential of dioxin leaching to groundwater is much lower unless concentrations are really high,” Toor explained.

Still, the tests don’t address a bigger worry to many parents: what was the risk before the park was completely turfed over earlier this year?

“Kids eat sand. Whether you like it or not, they do,” said Dawn McCarthy, who took her 4-year-old and 7-month-old daughters to the park almost daily for play dates with a group of neighborhood moms. “When you’re dealing with whether kids were damaged, we have to be looking at the real potential, and that was before’’ the city installed artificial turf.

The Florida Department of Health received the report Tuesday and is speeding up its review to get a quick answer to questions, said Director of Environmental Health and Engineering Samir Elmir.

“We’re trying our best to expedite the review process,” he said. “This is a priority for us.”

The city intensified its testing of the park, tucked in the center Grove, last month after a wider study raised concerns. More than two years ago, the city discovered contamination at its old municipal incinerator, about a mile away, which is now home to a firefighters’ training facility.

The county ordered the city to address the problem, but the city failed to do so until residents began complaining. In addition to testing around the training facility, the county demanded sampling within a mile radius, including area parks. Most turned up clean, except Blanche and Merrie Christmas Park, which the county ordered closed and fenced off while it’s being studied.

Initially, workers sampling Blanche Park found elevated levels of arsenic and buried ash in the center of the park. The city briefly closed the park and paved over the parking lot, assuring residents the artificial turf provided a safe cap. The city installed the turf in the dog park about two years ago and finished the turf in the playground earlier this year, said Miami City Commissioner Marc Sarnoff.

Because consultants have not yet figured out the boundaries of the contamination, they were continuing to take samples on Wednesday, Sarnoff said.

“They’re looking for the edge of the remnant ash, for where it stops. That’s the last piece of the puzzle: where is the northern edge of the remnant ash,” he explained.

“The answer is still going to be same for park, but the question is what if the remnant ash is beyond the park?” Sarnoff said. “Because then you have houses.”

While testing continues, another park, Lincoln Park at 2950 Jackson Ave., is being spruced up with new playground equipment to accommodate parents, Sarnoff said. The park, he said, has already been tested and given a clean bill of health.